CN112638572A

CN112638572A - Gas protection device for laser processing head

Info

Publication number: CN112638572A
Application number: CN201980056581.1A
Authority: CN
Inventors: 尤里·V·马库斯霍夫; 尼吉特·N·奈尔; 弗兰克·L·杜比克; 尤里·格拉普夫
Original assignee: IPG Photonics Corp
Current assignee: IPG Photonics Corp
Priority date: 2018-08-30
Filing date: 2019-08-30
Publication date: 2021-04-09
Also published as: KR20210042398A; CA3110532A1; EP3826802A1; JP7444854B2; EP3826802A4; SG11202101941VA; JP2021536366A; WO2020047454A1; US20200070283A1

Abstract

The gas shield apparatus may be used with a laser processing head, such as a welding head, to spread and distribute a shield gas over a larger gas shielded area for shielding a larger metal area. The gas shield may be coupled to the laser processing head to move with the laser beam and may be arranged coaxially to provide greater shielding effect in all welding directions. The gas shield is particularly suitable for welding titanium or other metals that are highly reactive with gases in the air and/or for larger welding areas (e.g., in the case of laser beam flutter).

Description

Gas protection device for laser processing head

Cross Reference to Related Applications

The present application claims priority from U.S. provisional application serial No.62/725,028, entitled gas shield for use with a laser processing head, filed 2018, 8, 30, which is hereby incorporated by reference in its entirety.

Technical Field

The present invention relates to laser machining and, more particularly, to a gas shield apparatus for use with a laser machining head.

Background

Lasers such as fiber lasers are commonly used for material processing applications such as welding. A conventional laser welding head includes a collimator for collimating the laser light and a focusing lens for focusing the laser light to a target area to be welded. The beam may be moved in various patterns to facilitate welding of the two structures, for example, using near field scanning or "wobbler" techniques. Various techniques may be used to move the beam, including rotating the beam using rotating prism optics to form a rotating pattern or a spiral pattern, and pivoting or moving the entire weld head on an X-Y stage to form a zigzag pattern. Other techniques for moving the light beam more quickly and more accurately include, for example, using movable mirrors to provide a dithered pattern of the light beam, as disclosed in greater detail in U.S. patent application publication No.2016/0368089 and international publication WO 2017/139769, which are commonly owned and hereby incorporated by reference in their entirety.

A shielding gas, such as an inert gas or a semi-inert gas, is typically used during laser welding to protect the weld area from atmospheric gases such as oxygen and water vapor and/or to suppress weld plume (weld plume). For example, as shown in fig. 15, conventional gas shielding uses a single nozzle to apply a gas flow to the laser weld area. As shown in fig. 16, a coaxial nozzle may be attached to the welding head as an attachment to provide shielding gas to the weld site. Such protection may not be sufficient because the nozzle in fig. 15 is separate from the laser welding head, and because the nozzles in fig. 15 and 16 may not provide a sufficiently large protection effect.

For example, greater protective effects may be required when scanning a laser beam to provide a dithered pattern or for certain welding applications. For example, when welding alloys like aluminum, copper and titanium, better protection is needed because these alloys react easily with oxygen, nitrogen and carbon dioxide. If these molten metals are not adequately protected from air, welding may result in brittle structures that degrade the mechanical properties of the welded joint and may cause discoloration in the joint. In particular, titanium is very reactive with gases in air and should be protected at temperatures above 350 ℃.

Disclosure of Invention

According to one aspect of the invention, a gas shield apparatus for use with a laser processing head is provided. The gas-protecting device includes a neck defining a central aperture extending from a first end to a second end of the neck. The central aperture is configured to receive a laser beam from the first end through the second end to the workpiece. The protection plate is coupled to the neck near the second end such that the neck extends from the first side of the protection plate and the protection plate extends circumferentially around the central aperture. The protective plate includes a plurality of gas outlets on the second side of the protective plate that are fluidly coupled to the at least one gas inlet and configured to direct a flow of gas in a direction toward the surface of the workpiece at a plurality of locations.

According to another aspect of the invention, a protected laser welding head comprises: a scanning laser welding head device configured to be coupled to an output fiber of the fiber laser and configured to move the laser beam only within a limited field of view, and a gas shield device coupled with the laser welding head device. The gas-protecting device includes a neck defining a central aperture extending from a first end to a second end of the neck. The central aperture is configured to receive a moving laser beam from the first end through the second end to a workpiece. The protective plate is coupled to the neck such that the neck extends from a first side of the protective plate and the protective plate extends circumferentially around the central aperture. The protective plate includes a plurality of gas outlets on a second side opposite the first side, wherein the plurality of gas outlets are fluidly coupled to at least one gas inlet and configured to direct a flow of gas in a direction toward a surface of the workpiece at a plurality of locations.

According to another aspect of the present invention, a laser welding system includes: the laser system includes a fiber laser including an output fiber, a laser coupled to the output fiber of the fiber laser and configured to move a laser beam scanning laser welding head within only a limited field of view, and a gas shield coupled to the laser welding head. The gas-protecting device includes a neck defining a central aperture extending from a first end to a second end of the neck. The central aperture is configured to receive a moving laser beam from the first end through the second end to a workpiece. A protective plate is coupled to the neck such that the neck extends from a first side of the protective plate and the protective plate extends circumferentially around the central aperture. The protective plate includes a plurality of gas outlets on a second side opposite the first side. The plurality of gas outlets are fluidly coupled to the at least one gas inlet and configured to direct a flow of gas in a direction toward a surface of the workpiece at a plurality of locations.

Drawings

These and other features and advantages will be better understood from a reading of the following detailed description in conjunction with the drawings, in which:

FIG. 1 is a schematic block diagram of a system including a laser welding head with a gas shield apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic illustration of a focused laser beam having a relatively small range of movement provided by a dual mirror for dithering (wobbling) purposes, in accordance with an embodiment of the present invention.

Fig. 3A to 3D are schematic diagrams illustrating different dither patterns (wobbble patterns) that can be generated by a welding head including a double mirror for beam movement according to an embodiment of the present invention.

Fig. 4 and 5 are perspective views of exemplary embodiments of a laser welding head having a collimator module, a vibrator (vibrator) module, and a core block module assembled together and emitting a focused beam.

FIG. 6 is a bottom perspective view of a gas-protecting apparatus according to an embodiment of the invention.

Fig. 7 is a side view of the gas-protecting apparatus shown in fig. 6.

Fig. 8 is a bottom view of the gas-protecting apparatus shown in fig. 6.

FIG. 9 is a top perspective view of the gas-protecting apparatus shown in FIG. 6.

FIG. 10 is a cut-away perspective view of the gas-protecting apparatus shown in FIG. 6.

FIG. 11 is a cross-sectional side view of the gas-protecting apparatus shown in FIG. 6.

12A and 12B are photographs showing a top perspective view and a bottom perspective view of a gas protection device coupled to a gas distribution tube according to an embodiment of the invention.

13A and 13B are photographs showing a top perspective view and a bottom perspective view of a gas protection device coupled to a gas distribution tube according to another embodiment of the invention.

FIG. 14 is a side perspective view of the gas-protecting apparatus shown in FIGS. 13A and 13B.

Fig. 15 is a schematic view of a conventional gas protecting apparatus using a single nozzle.

FIG. 16 is a perspective view of a conventional coaxial nozzle for delivering shielding gas coaxially to a weld site.

Detailed Description

According to embodiments of the present disclosure, a gas shielding device (gas shielding device) may be used with a laser processing head, such as a welding head, to spread and distribute shielding gas over a larger area of gas shielding to shield a larger area of metal. The gas shield may be coupled to the laser processing head to move with the laser beam and may be arranged coaxially to provide greater shielding in all directions of welding. The gas shield apparatus is particularly useful for welding titanium or other metals that are highly reactive with gases in air and/or for larger weld areas (e.g., in the case of laser beam chatter).

In some embodiments, the gas shield apparatus may be used with a laser welding head with a movable mirror (movable mirrors) that performs a welding operation, such as in a dithered pattern. The movable mirror provides a dithering motion of one or more light beams within a relatively small field of view, defined by a scan angle of 1-2, for example. The movable mirror body may be a galvanometer mirror (galvometers) that may be controlled by a control system including a galvo controller. The control system may also be used to control the fiber laser, for example in response to the position of the beam relative to the workpiece and/or sensed conditions in the weld head (such as thermal conditions proximate to one of the mirrors).

Referring to fig. 1, a laser welding system 100 includes a laser welding head 110 and a gas protection device 150, the laser welding head 110 being coupled (e.g., by a connector 111a) to an output fiber 111 of a fiber laser 112 for delivering a laser beam 118 to a workpiece 102, the gas protection device 150 being coupled to a gas source 151 by at least one gas distribution tube 152. The gas shield 150 may be generally coaxial with the laser beam 118 to allow passage of the laser beam 118 to the workpiece 102 while diffusing and distributing the shielding gas 153 around the laser beam 118 and throughout the entire weld area, as described in more detail below. The shielding gas 153 may include any shielding gas used in welding or laser machining, such as inert gases and semi-inert gases.

The laser welding head 110 may be used to perform welding on the workpiece 102, such as by welding the seam 104 to form a weld bead 106(weld bead). The laser welding head 110 and/or the workpiece 102 may be moved relative to each other in the direction of the seam 104. The laser welding head 110 may be positioned on a motion stage 114 to move the welding head 110 relative to the workpiece 102 along at least one axis, such as along the length of the seam 104. Additionally or alternatively, the workpiece 102 may be positioned on a motion stage 108 to move the workpiece 102 relative to the laser welding head 110.

The fiber laser 112 may comprise an ytterbium fiber laser capable of lasing in the near infrared spectral range (e.g., 1060-1080 nm). The ytterbium fiber laser may be a single mode or multi-mode continuous wave ytterbium fiber laser capable of producing laser beams up to 1kW of power in some embodiments and up to 50kW of higher power in other embodiments. Examples of the fiber laser 112 include a YLR SM series laser or a YLR HP series laser available from IPG Photonics Corporation. The fiber laser 112 may also include a multi-beam fiber laser, such as the type disclosed in international application No. pct/US2015/45037 entitled multi-beam fiber laser system filed on 8/13/2015, which is capable of selectively delivering one or more laser beams through a plurality of optical fibers.

The laser welding head 110 generally includes a collimator 122 for collimating the laser beam from the output fiber 111, at least first and second

movable mirrors

132, 134 for reflecting and moving the collimated beam 116, and a focusing lens 142(lens) for focusing and delivering the focused beam 118 to the workpiece 102. In the illustrated embodiment, the fixed mirror 144 also serves to direct the collimated laser beam 116 from the second movable mirror 134 to the focusing lens 142. The collimator 122, the

movable mirrors

132, 134, and the focusing lens 142 and the fixed mirror 144 may be provided in

separate modules

120, 130, 140 that can be coupled together, as described in more detail below. The laser welding head 110 can also be configured without a fixed mirror 144, for example, if the

mirrors

132, 134 are arranged such that light is reflected from the second mirror 134 towards the focusing lens 142.

The

movable mirrors

132, 134 can be pivoted about

different axes

131, 133 to move the collimated beam 116, and thus the focused beam 118, relative to the workpiece 102 on at least two different vertical axes 2, 4. The

movable mirrors

132, 134 may be galvanometer mirrors (galvano meters) movable by galvo motors (galvo motors), which can reverse direction quickly. In other embodiments, other mechanisms, such as stepper motors, may be used to move the mirror. The use of

movable mirrors

132, 134 in the laser welding head 110 allows the laser beam 118 to be moved accurately, controllably, and rapidly for beam flutter purposes without having to move the entire welding head 110 and without the use of rotating prisms.

In one embodiment of the weld head 110, as shown in FIG. 2, the

movable mirrors

132, 134 move the beam 118 only within a relatively small field of view (e.g., less than 30x30mm) by pivoting the beam 118 within a scan angle α of less than 10, and more particularly within a scan angle α of about 1-2, thereby allowing the beam to dither. In contrast, conventional laser scanning heads generally provide movement of the laser beam over a larger field of view (e.g., greater than 50x50mm and as large as 250x250 mm) and are designed to accommodate larger field of views and scanning angles. Thus, the use of

movable mirrors

132, 134 to provide only a relatively small field of view in the laser welding head 110 is counter intuitive and runs counter to the conventional insight of providing a wider field of view when using galvanometer scanners (galvo scanners). Limiting the field of view and scan angle when using galvanometer mirrors (galvo mirrors) in the welding head 110 provides advantages, for example, by allowing faster speeds, allowing the use of less expensive components (e.g., lenses), and allowing the use of accessories (e.g., air knives and/or gas assist fittings).

Due to the smaller field of view and scan angle in the exemplary embodiment of the weld head 110, the second mirror 134 may be substantially the same size as the first mirror 132. In contrast, conventional galvanometer scanners typically use a larger second mirror to provide a larger field of view and scan angle, and the larger second mirror limits the speed of movement in at least one axis. Thus, the smaller size of the second mirror 134 in the weld head 110 (e.g., approximately the same size as the first mirror 132) enables the mirror 134 to move at a faster speed than the larger mirror in a conventional galvanometer scanner that provides a larger scan angle.

The focusing lens 142 may comprise focusing lenses known to be used for laser welding heads and having various focal lengths, for example, in the range of 100mm to 1000 mm. Conventional laser scanning heads use multi-element scanning lenses, such as F theta lenses (F theta lenses), field flattening lenses (field flattening lenses), or telecentric lenses (telecentric lenses), which have larger diameters (e.g., 300mm diameter lenses for 33mm diameter beams) to focus the beams over a larger field of view. Because the

movable mirrors

132, 134 move the beam within a relatively small field of view, a larger multi-element scanning lens (e.g., an F θ lens) is not required and is not used. In one exemplary embodiment of a bond head 110 according to the present invention, a plano convex (plano concave) F300 focusing lens with a diameter of 50mm may be used to focus a beam with a diameter of about 40mm to move within a field of view of about 15 x5 mm. The use of a smaller focusing lens 142 also allows for the use of additional attachments at the end of the solder head 110, such as an air knife (air knife) and/or a gas assist attachment (gas assist attachments). The larger scan lens required by conventional laser scanning heads limits the use of such assemblies.

Other optical components may also be used in the laser welding head 110, such as a beam splitter for splitting the laser beam to provide at least two spots for welding (e.g., on each side of the weld). Additional optics may also include diffractive optics and may be located between the collimator 122 and the

mirrors

132, 134.

A protective window 146 may be provided in front of the lens 142 to protect the lens and other optics from debris generated during the soldering process. The protective window 146 may also be integrated into the gas protection device 150 or replaced by the gas protection device 150. The laser welding head 110 with the movable mirror can be used with welding head attachments such as the gas shield 150 and other existing laser welding attachments.

The illustrated embodiment of the laser welding system 100 also includes a detector (not shown), such as a camera, for detecting and positioning the seam 104, for example, at a location in front of the beam 118. The camera/detector may be located at one side of the welding head 110 or may be directed through the welding head 110 to detect and locate the seam 104. An additional light source (not shown) may be used with the camera as this may be required due to being shielded by the gas shielding device 150.

The illustrated embodiment of the laser welding system 100 also includes a control system 160 for controlling the positioning of the fiber laser 112, the

movable mirrors

132, 134, and/or the motion stages 108, 114, for example, in response to sensed conditions in the welding head 110, the detected position of the seam 104, and/or the movement and/or position of the laser beam 118. The laser welding head 110 may include sensors, such as first and second

thermal sensors

162, 164, the first and second

thermal sensors

162, 164 being proximate to the respective first and second

movable mirrors

132, 134 to sense thermal conditions. The control system 160 is electrically connected to the

sensors

162, 164 for receiving data to monitor thermal conditions in the vicinity of the

movable mirrors

132, 134. The control system 160 may also monitor the welding operation by receiving data (e.g., data representative of the detected position of the joint 104) from a camera/detector (not shown).

The control system 160 may control the fiber laser 112, for example, by turning off the laser, changing a laser parameter (e.g., laser power), or adjusting any other laser parameter that can be adjusted. The control system 160 may turn off the fiber laser 112 in response to the sensed condition in the laser welding head 110. The sensed condition may be a thermal condition that is sensed by one or both of the

sensors

162, 164 and is indicative of a mirror failure resulting in a high temperature or other condition caused by the high power laser.

The control system 160 may turn off the fiber laser 112 by triggering a safety interlock. A safety interlock is configured between output fiber 111 and collimator 122 such that when output fiber 111 is disconnected from collimator 122, a safety interlock condition is triggered and the laser is turned off. In the illustrated embodiment, the laser welding head 110 includes an interlock path 166 that extends the safety interlock feature to the

movable mirrors

132, 134. An interlock path 166 extends between the output fiber 111 and the control system 160 to allow the control system 160 to trigger a safety interlock condition in response to a potentially dangerous condition detected in the laser welding head 110. In this embodiment, the control system 160 may cause a safety interlock condition to be triggered via the interlock path 166 in response to a predetermined thermal condition detected by one or both of the

sensors

162, 164.

The control system 160 may also control a laser parameter (e.g., laser power) in response to movement or position of the beam 118 without turning off the laser 112. If one of the

movable mirrors

132, 134 moves the beam 118 out of range or too slowly, the control system 160 can reduce the laser power to dynamically control the energy of the spot to avoid damage caused by the laser. The control system 160 may further control the selection of laser beams in the multi-beam fiber laser.

The control system 160 may also control the positioning of the

movable mirrors

132, 134 in response to the detected position of the seam 104 from the camera/detector, e.g., to correct the position of the focused beam 118 to find, track, and/or follow the seam 104. The control system 160 may find the seam 104 by identifying the location of the seam 104 using data from the camera/detector, and then moving one or both of the

mirrors

132, 134 until the beam 118 coincides with the seam 104. The control system 160 may follow the seam 104 by moving one or both of the

mirrors

132, 134 to continuously adjust or correct the position of the beam 118 so that the beam coincides with the seam 104 as the beam 118 moves along the seam to perform welding. The control system 160 can also control one or both of the

movable mirrors

132, 134 to provide a dithering motion during welding, as described in more detail below.

Thus, the control system 160 includes both laser control and mirror control working together to control both laser and mirror together. The control system 160 may include, for example, known hardware (e.g., a general purpose computer) and software for controlling fiber lasers and galvanometer mirrors (galvo mirrors). For example, existing galvanometer (galvo) control software may be used and modified to allow the galvanometer mirror to be controlled as described herein. For example, the control system 160 may further control the gas source 151 to control the pressure of the shielding gas delivered to the gas shielding device 150 through the gas distribution conduit 152.

Fig. 3A-3D illustrate examples of flutter patterns that may be used to perform stir welding (still welding) of the seam 304. As used herein, "dither" refers to the reciprocating motion of a laser beam (e.g., on two axes) and within a relatively small field of view defined by a scan angle of less than 10 °. Fig. 3A and 3B illustrate a circular pattern and a figure 8 pattern, respectively, that are sequentially formed along the seam 304. Fig. 3C and 3D show a zigzag pattern and a wavy pattern, respectively, formed along the seam 304. Although certain dither patterns are shown, other dither patterns are within the scope of the present invention. One advantage of using a movable mirror in the laser welding head 110 is the ability to move the beam according to a variety of different dither patterns.

Fig. 4 and 5 illustrate an exemplary embodiment of the scanning laser welding head 410 in more detail. While one specific embodiment is shown, other embodiments of the laser welding head and systems and methods described herein are also within the scope of the invention. As shown in fig. 4, the laser welding head 410 includes a collimator module 420, a ditherer module 430 and a core block module 440. The vibrator module 430 includes first and second movable mirrors as described above and is coupled between the collimator module 420 and the pellet module 440.

The collimator module 420 may include a collimator (not shown) having a pair of fixed collimator lenses, such as of the type known to be used in laser welding heads. In other embodiments, the collimator may include other lens configurations that enable adjustment of the spot size and/or focus, such as a movable lens. The ditherer module 430 may include first and second galvanometers (not shown) for moving galvanometer mirrors (not shown) about different vertical axes. Known galvanometers used for laser scanning heads may be used. The galvanometer may be connected to a galvo controller (not shown). The galvanometer controller may include hardware and/or software for controlling the galvanometer to control movement of the mirror and, in turn, movement and/or positioning of the laser beam. Known galvanometer mirror (galvo mirrors) control software may be used and may be modified to provide the functions described herein, such as seam finding, ditherer pattern generation, and communication with the laser. The core block module 440 may include a fixed mirror (not shown) that redirects the light beam received from the dither module 430 to a focusing lens and then to the workpiece.

Fig. 4 and 5 show a laser welding head 410 assembled with each of the

modules

420, 430, 440 coupled together and emitting a focused beam 418. The laser beam coupled into the collimator block 420 is collimated, and the collimated beam is guided to the pulsator block 430. The vibrator module 430 moves the collimated beam using a mirror and directs the moved collimated beam to the core block module 440. The moving beam is then focused by the core block module 440, and the focused beam 418 is directed to a workpiece (not shown).

Referring to fig. 6-12, an exemplary embodiment of a gas protection device 600 is shown and described in more detail. This embodiment of the gas shield apparatus 600 includes a neck 610 for applying a laser beam (e.g., as described above) to a workpiece by scanning, and a gas shield plate 620 coupled to the neck 610 for diffusing and distributing a shield gas to the workpiece in a welding region. The neck 610 defines a central aperture 612 that extends from the first end 611 to the second end 613, and the neck 610 is configured to allow a scanning laser beam to be directed through the protective plate 620 to a workpiece on the opposite side of the protective plate 620. A protective plate 620 is coupled to the neck 610 near the second end 613 and extends circumferentially around the central aperture 612 such that the protective plate 620 is coaxial with the central aperture 612 that receives the scanned laser beam. The central aperture 612 in the neck 610 may have a diameter in the range of about 10-60 mm.

In this embodiment, the protective plate 620 includes one or more gas inlets 622 on a first surface 621 and a plurality of gas outlets 624 on a second surface 623, the second surface 623 being opposite the first surface 621 and facing the workpiece during use. The protective plate 620 defines a gas diffusion region 626 that fluidly couples the gas inlet 622 to the plurality of gas outlets 624. In one embodiment, the gas diffusion region 626 may comprise a porous material (e.g., available from 3M under the designation "Scotch-Brite^TMA non-woven mat of universal scouring Pads (scout Pads) "), or any other diffuser material capable of providing a laminar distribution from the gas outlet 624.

As indicated by the arrows in fig. 11, the shielding gas enters the gas diffusion region 626 through the gas inlet 622 and then exits the gas outlet 624 toward the workpiece 602, e.g., in a direction generally perpendicular to the surface of the workpiece 602. In this way, the protective plate 620 and the gas outlet 624 are designed and configured to diffuse the shielding gas and provide a laminar flow of the shielding gas in the process or welding area.

As shown in the illustrated embodiment, the gas outlets 624 may be distributed over a substantial portion of the second side 623 of the shield plate 620 to distribute the shield gas over a relatively wide area including at least the scan area of the laser beam and the machining or welding area. Examples of the protective plate 620 may have a diameter in the range of about 100mm to 150mm, and more specifically about 100mm, about 125mm, or about 150 mm. Although the protective plate 620 is shown as a circular disk, other shapes are also contemplated, including but not limited to polygonal shapes and rectangular/oblong shapes. Providing a coaxial arrangement allows good protection in any direction relative to the laser beam at the welding area.

Each of the gas outlets 624 may be a relatively small hole or opening, for example, a hole or opening having a diameter in the range of approximately 0.2-5.0 mm. The gas outlets 624 are distributed in a pattern on the second side 623 of the protective plate 620 to provide sufficient diffusion to produce a laminar flow of the protective gas. In the illustrated embodiment, the pattern includes gas outlets 624 arranged in lines extending from a central portion of the protective plate 620 (e.g., near the central aperture 612) to an outer portion of the protective plate 620. Other patterns of gas outlets 624 are also contemplated, including but not limited to concentric circles and radial lines. The gas outlets 624 may also be substantially evenly distributed over the second surface 623 of the gas protection plate 620.

Although the illustrated embodiment shows four (4) gas inlets 622 distributed substantially evenly around the first surface 621 of the protection plate 620, other numbers and locations of gas inlets 622 are contemplated. In other embodiments, the gas inlet 622 may also be located in other locations, such as on the neck 610. The gas inlet 622 may be coupled to a gas pipe 630, for example, as shown in fig. 12A and 12B. The size, number, and location of the gas inlets and gas outlets, as well as the gas pressure, may be varied to provide the desired laminar flow. As shown in fig. 12B, the bottom neck portion 616 defining the central aperture 612 may extend beyond the protective plate 620.

The gas shield apparatus 600 may be coupled to the scanning laser welding head 400 described herein or any other laser welding head or laser machining head. This embodiment of the gas-protecting device 600 may be coupled coaxially with the laser processing head. The gas-shielding device 600 may be coaxially coupled to the laser processing head using a coupling mechanism 650, the coupling mechanism 650 being similar to coupling mechanisms used with existing coaxial nozzles, for example, as shown in fig. 16. By coupling the gas-protecting device 600 to the laser processing head, the gas-protecting device 600 and the greater protecting effect move with the scanning laser beam and the need to control two separate devices is avoided.

Another embodiment 1300 of a gas-protecting apparatus is shown in fig. 13A, 13B and 14. In this embodiment, the gas shield apparatus 1300 includes a gas shield plate 1320 and a neck 1310, the neck 1310 including one or more cooling channels to provide a water (or other liquid) cooling function that allows continuous operation without overheating. One or more cooling inlets/outlets 1340 are coupled to a top portion 1318 of the neck 1310 to allow water or other cooling fluid to enter and exit the cooling channels. In this embodiment, similar to the embodiments described above, the neck 1310 defines a central orifice 1312 and the gas shield plate 1320 defines a plurality of gas outlets 1324.

In this embodiment 1300 of the gas-protecting apparatus, the gas inlet 1322 is also located on the top portion 1318 of the neck 1310, and the gas channel extends through the neck to the gas outlet 1324 on the bottom of the protective plate 1320. As described above, the coupling mechanism 1350 may be used to couple the top portion 1318 of the neck 1310 to the welding head. The bottom neck portion 1316 also defines a central aperture 1312 and extends from the bottom of the protective plate 1320.

To accommodate the cooling channels and gas channels, the neck 1310 of the gas-protecting device 1300 has a larger diameter than the embodiments described above. In one example, the neck 1310 has a diameter of about 76.2mm, the protective plate 1320 has a diameter of about 128mm, the top portion 1318 of the neck 1310 has a diameter of about 95mm, the coupling mechanism 1350 has a diameter of about 39.5mm, and the bottom neck portion 1316 has a diameter of about 42 mm. In this embodiment, the neck 1310 may include an outer tube and an inner tube (not shown) with the cooling channel and the gas channel located therebetween. The inner tube may be made of stainless steel (i.e., as opposed to aluminum).

Thus, according to embodiments disclosed herein, the gas shield apparatus provides an effective gas shield over a wider area surrounding the laser machining area, which is particularly advantageous for flutter welding applications for materials that are sensitive to or react with oxygen or nitrogen.

While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. In addition to the exemplary embodiments shown and described herein, other embodiments are also within the scope of the present invention. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is limited only by the following claims.

Claims

1. A gas shield for use with a laser processing head, the gas shield comprising:

a neck defining a central aperture extending from a first end to a second end of the neck, wherein the central aperture is configured to receive a laser beam from the first end through the second end to a workpiece; and

a protective plate coupled to the neck near the second end such that the neck extends from a first side of the protective plate and the protective plate extends circumferentially around the central aperture, the protective plate including a plurality of gas outlets on a second side of the protective plate, wherein the plurality of gas outlets are fluidly coupled to at least one gas inlet and configured to direct a flow of gas in a direction toward a surface of the workpiece at a plurality of locations.

2. The gas protection device of claim 1, wherein the at least one gas inlet is located at the first side of the protection plate.

3. The gas protection device of claim 1, wherein the at least one gas inlet is located on a top portion of the neck.

4. The gas protection device of claim 1, further comprising at least one gas distribution tube coupled to the at least one gas inlet, the at least one gas distribution tube for distributing a shielding gas to the plurality of gas outlets on the second side.

5. The gas protection device of claim 1, wherein the neck includes at least one cooling channel and at least one cooling inlet/outlet coupled to the cooling channel to allow a cooling fluid to flow through the cooling channel.

6. The gas-protecting device of claim 1, wherein the protective plate is circular in shape.

7. The gas-protecting device of claim 6, wherein the protective plate has a diameter in the range of 100mm to 150 mm.

8. The gas-protecting device of claim 1, wherein the protective plate is coaxial with the neck and the central aperture.

9. The gas shield apparatus of claim 1 wherein the neck includes a processing head coupling mechanism at a first end of the neck for coupling to a laser processing head.

10. The gas shield apparatus of claim 1, wherein the plurality of gas outlets are formed along a line extending outwardly from a central portion of the protective plate to an outer portion of the protective plate.

11. The gas shield apparatus of claim 1, wherein the plurality of gas outlets are arranged to provide a laminar flow of gas that surrounds the moving laser beam that passes through the shield plate to the workpiece.

12. The gas protection device of claim 1, wherein the central orifice has a diameter in the range of 10-60 mm.

13. The gas protection device of claim 1, wherein the protective plate comprises a porous material between the at least one gas inlet and the gas outlet.

14. A protected laser welding head comprising:

a scanning laser welding head device configured to be coupled to an output fiber of a fiber laser and configured to move a laser beam only within a limited field of view; and

a gas shield device coupled with a laser welding head device, the gas shield device comprising:

a neck defining a central aperture extending from a first end to a second end of the neck, wherein the central aperture is configured to receive a moving laser beam from the first end through the second end to a workpiece; and

a protective plate coupled to the neck such that the neck extends from a first side of the protective plate and the protective plate extends circumferentially around the central aperture, the protective plate including a plurality of gas outlets on a second side opposite the first side, wherein the plurality of gas outlets are fluidly coupled to at least one gas inlet and configured to direct a flow of gas in a direction toward a surface of the workpiece at a plurality of locations.

15. The laser welding head of claim 14 wherein the limited field of view is defined by a scan angle of approximately 1-2 °.

16. The laser welding head of claim 14 wherein the laser welding head device comprises:

a collimator;

at least first and second movable mirrors configured to receive the collimated laser beam from the collimator and move the beam in a first axis and a second axis within a limited field of view; and

a focusing lens configured to focus the laser beam relative to the workpiece while the beam is moved.

17. The laser welding head of claim 16 wherein the movable mirror is a galvanometer mirror.

18. The laser welding head of claim 16 wherein the movable mirror is configured to move the collimated laser beam only within a limited field of view having a size of less than 30x30 mm.

19. A laser welding system, comprising:

a fiber laser including an output fiber;

a scanning laser welding head coupled to the output fiber of the fiber laser and configured to move a laser beam only within a limited field of view;

a gas shield device coupled to a laser welding head, the gas shield device comprising:

a protective plate coupled to the neck such that the neck extends from a first side of the protective plate and the protective plate extends circumferentially around the central aperture, the protective plate including a plurality of gas outlets on a second side opposite the first side, wherein the plurality of gas outlets are fluidly coupled to at least one gas inlet and configured to direct a flow of gas in a direction toward a surface of the workpiece at a plurality of locations; and

a control system for controlling at least the position of the fiber laser and the mirror.

20. The laser welding system of claim 19 wherein the fiber laser comprises an ytterbium fiber laser.

21. The laser welding system of claim 19 wherein the fiber laser includes a plurality of output fibers for delivering a plurality of laser beams.

22. The laser welding system of claim 19 wherein the control system is configured to control movement of the moving laser beam within the limited field of view to provide a dithered pattern.